Last month, Mirage notified its two partners in the project, Circus Circus Enterprises Inc. and Boyd Gaming Corporation, that it planned to build the resort on its own. Boyd sued Mirage on Feb. 2.

In the latest lawsuit, Circus Circus contended that Mirage had aligned itself with partners to make it easier to persuade the State of New Jersey to construct a $350-million tunnel and roadway connecting the Atlantic City Expressway with the resort complex. ''Having capitalized on Circus's efforts and good will, Mirage dumped Circus as its partner,'' Circus Circus said in the complaint filed in Atlantic County Superior Court. The lawsuit also accuses Mirage of unjustly receiving ''a private, oversized driveway to a casino-hotel that has no immediate competition.''

Alan M. Feldman, a spokesman for Mirage, said he would have no comment until after company officials had seen the lawsuit.